docs: def unpack(self, unpacker):
          """
          unpacks a code block from a buffer. Updates the internal structure
          of this instance
          """
  
          (a, b, c) = unpacker.unpack_struct(_HHI)
  
          self.max_stack = a
          self.max_locals = b
          self.code = unpacker.read(c)
  
          uobjs = unpacker.unpack_objects
          self.exceptions = tuple(uobjs(JavaExceptionInfo, self))
  
          self.attribs.unpack(unpacker)